Connecting Education and Research

Spiders understand the “music” of their web

The sound of a spi­der web, plucked like a gui­tar string, pro­vides its in­hab­i­tants with in­forma­t­ion about prey, mates, and even we­b’s struc­tur­al con­di­tion, sci­en­tists have found.

The spi­ders use that qual­ity by “tun­ing” the silk, they say: con­trol­ling and ad­just­ing its prop­er­ties, and threads’ ten­sions and in­ter­con­nec­tiv­i­ties.

The find­ing comes from re­search­ers from the Uni­vers­i­ties of Ox­ford, Strath­clyde, and Shef­field in the U.K., who fired bul­lets and lasers at spi­der silk to study how it vi­brates. They found that un­like many oth­er ma­te­ri­als, spi­der silk is tun­a­ble to a wide range of har­mon­ics, or sim­ple pitch rela­t­ion­ships.

The find­ings, to be re­ported in the jour­nal ”Ad­vanced Ma­te­ri­als”, not only re­veal more about spi­ders but could al­so in­spire a wide range of new tech­nolo­gies, such as ti­ny light-weight sen­sors, the re­search­ers said.

“Most spi­ders have poor eye­sight and rely al­most ex­clu­sively on the vibra­t­ion of the silk in their web for sen­so­ry in­forma­t­ion,” said Beth Mor­ti­mer of the Ox­ford Silk Group at Ox­ford Uni­vers­ity, who led the re­search. “The sound of silk can tell them what type of meal is en­tan­gled in their net and about the in­ten­tions and qual­ity of a pro­spec­tive mate. By pluck­ing the silk like a gui­tar string and lis­ten­ing to the ‘e­choes’ the spi­der can al­so as­sess the con­di­tion of its we­b.”

To study the son­ic prop­er­ties of the spi­der’s gos­sa­mer threads the re­search­ers used ultra-high-speed cam­er­as to film the threads as they re­sponded to the im­pact of bul­lets. In ad­di­tion, lasers were used to make de­tailed mea­sure­ments of even the small­est vibra­t­ion.

“The fact that spi­ders can re­ceive these na­no­me­ter [millionth-of-a-millimeter] vibra­t­ions with or­gans on each of their legs, called slit sen­sil­lae, really ex­em­pli­fies the im­pact of our re­search about silk prop­er­ties found in our stu­dy,” said Shira Gor­don of the Uni­vers­ity of Strath­clyde, a co-au­thor of the re­port.

“These find­ings fur­ther dem­on­strate the out­stand­ing prop­er­ties of many spi­der silks that are able to com­bine ex­cep­tion­al tough­ness with the abil­ity to trans­fer del­i­cate in­forma­t­ion,” said Pro­fes­sor Fritz Voll­rath of the Ox­ford Silk Group at Ox­ford Uni­vers­ity, an au­thor of the pa­per. ‘These are traits that would be very use­ful in light-weight en­gi­neer­ing and might lead to nov­el, built-in ‘in­tel­li­gent’ sen­sors and ac­tu­a­tors.”

“Spi­der silks are well known for their im­pres­sive me­chan­i­cal prop­er­ties, but the vibra­t­ional prop­er­ties have been rel­a­tively over­looked and now we find that they are al­so an awe­some com­mu­nica­t­ion tool,” said Chris Hol­land of the Uni­vers­ity of Shef­field, anoth­er co-au­thor.

Added Mor­ti­mer: “It may even be that spi­ders set out to make a web that ‘sounds right’ as its son­ic prop­er­ties are in­ti­mately re­lat­ed to fac­tors such as strength and flex­i­bil­ity.”